Wireless communications in networked robotics - [guest editorial]

Over the last two decades, the success of wireless communications has exceeded our expectations, from both the marketing and technological aspects. It is evolving toward next-generation systems that will support wireless services in the most spectral and energy- efficient ways. At the same time, we have observed rapid technical advances in radio access. Among other areas, we would like to draw attention to the following aspects.     

Using mobile robots to harvest data from sensor fields - [wireless communications in networked robotics]

We explore synergies among mobile robots and wireless sensor networks in environmental monitoring through a system in which robotic data mules collect measurements gathered by sensing nodes. A proof-of-concept implementation demonstrates that this approach significantly increases the lifetime of the system by conserving energy that the sensing nodes otherwise would use for communication.     

Using robot mobility to exploit multipath fading - wireless communications in networked robotics

Communication-aware motion control allows mobile networked robots to increase the average communication throughput. We exploit that in a multipath fading channel, robots can measure the SNR and adapt their motion to spend slightly more time at positions where the channel is good. Two new such cross-layer strategies are analyzed and evaluated: periodic stopping, where the stop duration is a function of the SNR, and controlled stopping, where the robot stops when the communication buffer is filling up. It is shown that the expected average channel capacity can be twice as high as when no cross-layer information is utilized. Experimental evaluation of the strategies confirms the theoretical results.     

A networking framework for teleoperation in safety, security, and rescue robotics - [wireless communications in networked robotics]

Safety, security, and rescue robotics is an important application field that can be viewed as a prototypical example of a domain where networked mobile robots are used for the exploration of unstructured environments that are inaccessible to or dangerous for humans. Teleoperation, based on wireless networks, is much more complex than what one might expect at first glance because it goes well beyond mere mappings of low-level user inputs ? like joystick commands ? to motor activations on a robot. Teleoperation for SSRR must move up to the behavior and mission levels where a single operator triggers short-time, autonomous behaviors, respectively, and supervises a whole team of autonomously operating robots. Consequently, a significant amount of heterogeneous data ? video, maps, goal points, victim data, and so on ? must be transmitted between robots and mission control. In this article, a networking framework for teleoperation in SSRR is presented. It was evaluated in a series of field tests and competitions, including the European Land Robot Trials and RoboCup events.     

RF-mobility gain: concept, measurement campaign, and exploitation - [wireless communications in networked robotics]

Self-directed movement of radio devices can enable large amounts of power gain since the sources of fluctuations in received signal power due to multipath-induced small-scale fading have highly localized effects. We call the gain achieved by finding a better location the mobility gain. Experimental data for indoor as well as outdoor measurement studies are used to illustrate the potential of this RF-Mobility Gain concept over a wide range of frequencies. An analysis of the RF data reveals that a small amount of energy spent on searching for a better location can pay large dividends in long-term power expenditures for RF transmission. Challenges in building such a system for peer-to-peer links and network applications are discussed along with potential coordination algorithms.     

Coexistence of VoIP and TCP in wireless multihop networks - [topics in radio communications]

When supporting both voice and TCP in a wireless multihop network, there are two conflicting goals: to protect the VoIP traffic and to completely utilize the remaining capacity for TCP. We investigate the interaction between these two popular categories of traffic and find that many solution approaches, such as enhanced TCP variants, priority queues, bandwidth limitation, and traffic shaping, do not always achieve the coexistence goals. Enhanced TCP variants (Reno, Vegas, C-TCP, CUBIC, Westwood) generally fail to protect VoIP in wired-wireless multihop scenarios. Priority schemes, including those built into the 802.11 MAC such as RTS/CTS or 802.11e, do not account for the interference nature of wireless multihop. Finally, bandwidth shaping and window control are valid tools to control TCP, but come with their own trade-offs.     

Robosoccer [mobile robotics experiment]

This paper describes robosoccer, the latest experiment in robotics, and one that is growing in popularity on college campuses around the world. In robosoccer, two teams of boxy, wheeled robots face off against each other. A whistle blows and they spring into action, jostling for possession of a brightly colored golfball on a playing field the size ofa Ping-Pong table. Each team struggles to push the ball into the other team's goal located at the opposite end of the table. The author describes how the robots move fluidly and fluidly, constantly adjusting to the run of play in a surprisingly lifelike way     

The interplanetary Internet [networked space communications]

This paper discusses the current debate among NASA engineers on how to best achieve a networked model of interplanetary communications. While there are those who believe that existing Internet protocols can be extended deep into space, others believe that these Internet protocols need to be supplemented with new ones to network remote space.     

Standardization of femtocells in 3GPP - [femtocell wireless communications]

Cellular system operators have identified the critical need for standardization of femtocell devices and their associated interfaces into the operators' core networks as a critical requirement for the success of femtocell products. Driven by this demand, the UMTS/UTRAN standards community has been undertaking a large-scale and comprehensive effort to specify such standards for femtocell devices and systems that are based on the UMTS/HSDPA/HSUPA family of radio access technologies. This article describes those standardization activities and provides an overview for the femtocell system architecture that has been developed within 3GPP.     

Performance control in wireless sensor networks: the ginseng project - [Global communications news letter]

Research on wireless sensor networks (WSNs) has mainly been focused on protocols and architectures for applications in which network performance assurances are not considered essential, such as agriculture and environmental monitoring. However, for many important areas, such as plant automation and health monitoring, performance assurances are crucial, especially for metrics such as delay and reliability.     

Standardization of femtocells in 3GPP2 - [femtocell wireless communications]

Driven by the need for multivendor interoperability of femtocell devices and their supporting infrastructure equipment, the cdma2000reg standards community has been undertaking a large-scale and comprehensive effort to develop industry standards for femtocell devices and systems based on the cdma2000 family of radio access technologies. This article describes those standardization activities and provides an overview of the femtocell system architecture that has been developed within 3GPP2.     

System design of cdma2000 femtocells - [femtocell wireless communications]

Femtocells extend the cellular network coverage and provide high speed data service inside homes and enterprises for mobiles supporting existing cellular radio communication techniques. They also provide additional system capacity by offloading macro network traffic. This article reviews the characteristics of cdma2000-based femtocell systems. It discusses design and deployment aspects such as carrier allocation, access control, efficient support for femtocell discovery by idle mobiles, and active call hand-in from macrocell to femtocell. The evolution of the cdma2000 standard for optimizing performance and enriching user experience with femtocells is also discussed.     

Joint effort [mobile robot developments]

The author describes how distributed control has allowed British engineers to take a leap forward in the development of mobile robots for industrial applications     

Tree multicast strategies in mobile,multihop wireless networks

Tree multicast is a well established concept in wired networks. Two versions, persource tree multicast (e.g., DVMRP) and shared tree multicast (e.g., Core Based Tree), account for the majority of the wireline implementations. In this paper, we extend the tree multicast concept to wireless, mobile, multihop networks for applications ranging from ad hoc networking to disaster recovery and battlefield. The main challenge in wireless, mobile networks is the rapidly changing environment. We address this issue in our design by: (a) using soft state (b) assigning different roles to nodes depending on their mobility (2level mobility model); (c) proposing an adaptive scheme which combines shared tree and persource tree benefits, and (d) dynamically relocating the shared tree Rendezvous Point (RP). A detailed wireless simulation model is used to evaluate various multicast schemes. The results show that persource trees perform better in heavy loads because of the more efficient traffic distribution; while shared trees are more robust to mobility and are more scalable to large network sizes. The adaptive tree multicast scheme, a hybrid between shared tree and persource tree, combines the advantages of both and performs consistently well across all load and mobility scenarios. The main contributions of this study are: the use of a 2level mobility model to improve the stability of the shared tree, the development of a hybrid, adaptive persource and shared tree scheme, and the dynamic relocation of the RP in the shared tree.     

Early experiences and lessons learned from femtocells - [femtocell wireless communications]

There is a continuous pursuit by mobile operators (MOs) to improve indoor coverage in order not only to improve voice quality but also to enable higher data rates in home/office environments. Indoor coverage improvement, in conjunction with inexpensive (voice) offerings, will enable MOs to compete with and take away voice-call-related revenues from fixed network PTTs and/or VoIP operators. Femtocells constitute a promising solution to address all of the above. In this article we present our experience from our extensive study and trials of early (pre-standard) femtocell solutions that were available in the 2007-2008 timeframe.